$-9r - 8s + 6t + 3 = -7s - 7t - 6$ Solve for $r$.
Solution: Combine constant terms on the right. $-9r - 8s + 6t + {3} = -7s - 7t - {6}$ $-9r - 8s + 6t = -7s - 7t - {9}$ Combine $t$ terms on the right. $-9r - 8s + {6t} = -7s - {7t} - 9$ $-9r - 8s = -7s - {13t} - 9$ Combine $s$ terms on the right. $-9r - {8s} = -{7s} - 13t - 9$ $-9r = {s} - 13t - 9$ Isolate $r$ $-{9}r = s - 13t - 9$ $r = \dfrac{ s - 13t - 9 }{ -{9} }$ Swap the signs so the denominator isn't negative. $r = \dfrac{ -{1}s + {13}t + {9} }{ {9} }$